The utility of hydrogen as a transportation fuel is limited by safety and practicality concerns involving pressurized gas in a mobile vehicle. Thus, a practical hydrogen storage system paired with an efficient fuel cell can enable hydrogen as an alternative to liquid transportation fuels. One conceptual solution is to store hydrogen in small molecules such as MgH2, methanol, a hydrocarbon, or a boron-nitrogen compound. Particularly, ammonia-borane (AB, NH3BH3) is a promising material due to its high hydrogen content (19.6 wt %) and capacity to dehydrogenate under mild conditions. Several reports of transition metal catalyzed AB dehydrogenation have recently appeared. These involve rhodium, iridium, ruthenium, and nickel catalysts, among others. Among homogeneous systems, only Baker's Ni(NHC)2 catalysts have achieved both high productivity (>2.5 equivalents H2) and a useful rate (>10−3 s−1 at 60° C.).
Accordingly, there is a need for improved catalyst systems for dehydrogenating small molecules that store hydrogen.